A storage apparatus that is connected to host computers via a network comprises a plurality of magnetic disks, for example, as storage devices for storing data. The storage apparatus utilizes RAID (Redundant Array of Independent Disks) technology to establish redundancy of the storage areas of the plurality of storage devices and construct a RAID group. In addition, the storage apparatus provides the host computers with storage areas in the capacity required by the host computers and as logical volumes, from part of the RAID group.
Furthermore, if there is a data I/O request from the host computers, the storage apparatus executes exclusive extent processing, prior to executing the data I/O processing, so that there is no concurrent access to identical areas and to preserve the consistency of the access sequence. More specifically, exclusive extent processing is designed to prevent competing access to identical areas by determining whether or not there are I/O requests with overlapping extents (I/O request ranges) in the same logical volume among a plurality of I/O requests, and then if an overlap exists, awaiting I/O processing corresponding to the I/O requests, and if no overlap exists, continuing I/O processing corresponding to the I/O requests.
For example, PTL1 discloses an arrangement whereby, if an I/O request is sent to the storage apparatus, a control table of a logical volume targeted by the I/O request is locked and exclusive extent processing is executed.